The Asian carp may be a scene stealer, leaping out of the Mississippi River like popcorn
in a skillet, smacking boaters in the face, and starring in no end of slap-happy YouTube
videos. But for sheer destructive might, this algae-eating invader can't hold a candle
to a certain European mollusk about the size of a fat lima bean.

Michigan Tech biologist W. Charles Kerfoot got his first insights into the quagga
mussel back in 2001, when he and his research team were checking on a huge, green
ring dubbed "the doughnut" they'd discovered a few years earlier in southern Lake
Michigan.

No one knew about the doughnut, much less the quagga, until Kerfoot and his research
team first saw it in 1998. Using NASA's new Sea-viewing Wide Field-of-view Sensor
(SeaWiFS) Project, they saw a roughly circular river of phytoplankton—algae and other
tiny plants—that was drifting counterclockwise around the southern end of Lake Michigan,
creating a doughnut.

The group determined that the doughnut was formed when big winter storms kicked up
sediments along the southeastern shore of the lake. There, Michigan's biggest rivers
drain a watershed rich in phosphorus and other nutrients from cities and farms. Those
nutrients settle in the lake's sediments until storms stir them up. Then, suspended
in the water column, they begin circulating in a slow-moving gyre that flows from
Grand Haven in the north to Chicago in the south. That gyre creates a Thanksgiving
feast for phytoplankton. "We saw that with each storm, you get a ring, and it can
persist for weeks or even months," says Kerfoot.

"We were floating in the clouds, saying 'Hey, we discovered a new phenomenon,'" he
remembers. Samples of lake water taken from research vessels verified the satellite
data. Plus, they found that zooplankton, the tiny animals that feed on phytoplankton,
were much more abundant in the doughnut. For them, the seasonal bloom was an all-you-can-eat
salad bar, an important part of their strategy to survive winter. Those zooplankton
were eaten in turn by small fish, which were eaten by large fish, which fueled an
angling paradise productive enough to merit the nickname Lake Fishigan.

Then, almost as soon as it was discovered, the doughnut started to disappear. "Since
2001, the chlorophyll has been nibbled away on the edges, right where the quaggas
are," says Kerfoot.

The quagga mussel has been found in all of the Great Lakes, in all likelihood introduced
by ocean-going vessels when they dump their untreated ballast water. In addition to
clinging to hard surfaces like the more famous zebra mussel, quaggas also burrow into
soft lake bottoms, where they can be found in concentrations of 10,000 to 15,000 per
square meter. Their favorite food is phytoplankton, and they have prodigious appetites.
Hank Vanderploeg, a colleague of Kerfoot at the NOAA Great Lakes Research Laboratory,
calculated that they can filter up to one third of the water column in a day in the
band of water around the lake that's between thirty and fifty meters deep. There,
they are consuming five to seven times as much phytoplankton as is being produced.
"No surprise that it's that area that's cleaning up the most," Kerfoot says.

Using SeaWiFS, graduate student Foad Yousef has plotted a 75 percent decline in chlorophyll
a, a measure of phytoplankton abundance, from 2001 to 2008. "You are seeing a displacement
of productivity from the water column to the benthic layer," Kerfoot says. "It's fascinating."

That means that all the energy in the phytoplankton, which once fed fish, is being
sucked down to the bottom of the lake by quaggas, who then eject it in the form of
pseudo feces—mussel poop. That can stimulate the growth of Cladophora algae, which
die, decompose, and remove all the oxygen from the surrounding water, to ill effect.
"When things go anaerobic, that kills off everything, including the quaggas, and creates
conditions for botulism. We've had massive kills of fish-eating birds—loons, mergansers,"
says Kerfoot. "Isn't that bizarre? Who would have predicted that?"

Under such conditions, however, it is predictable that populations of zooplankton
will decline, and following them, the alewives, chubs, Atlantic salmon, muskies, smelt,
walleyes, perch, and the rest of the hundred or so species of fish that inhabit the
southern part of Lake Michigan. "A high percent of the fish biomass could be lost
in the next couple years," Kerfoot says. NOAA scientists have already documented declines
in several species. "We have a system that's crashing."

Why, then, isn't somebody doing something? Kerfoot was wondering himself, so he asked
the NOAA scientists who are charged with keeping their thumbs in the dike to protect
the Great Lakes from invasive creatures like the quaggas. "I asked why they weren't
swimming in money to do something about this," he says. "They say people are getting
tired of hearing that the sky is falling. Now, when the sky really is falling, they
aren't paying attention."

One exotic species Kerfoot isn't worried about is that Asian carp, which has all the
Great Lakes states up in arms for fear that it will enter the water system via the
Chicago Shipping Channel and destroy the fishery. Quaggas will have done that job
before the hundred-pound bottom feeders can even get a toehold, he says. "By the time
the carp get here, there won't be anything left for them to eat."

Funding for Kerfoot's research was provided by NOAA and the National Science Foundation.

Michigan Technological University is a public research university, home to more than
7,000 students from 54 countries. Founded in 1885, the University offers more than
120 undergraduate and graduate degree programs in science and technology, engineering,
forestry, business and economics, health professions, humanities, mathematics, and
social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway
and is just a few miles from Lake Superior.